The proposed research is an extention of an existing research project on adult crime and drug use. Focusing on the hardcore juvenile offender, the long term objectives orienting the study are to deal with two major gaps in current information about serious delinquency: what it actually looks like on the street today, and the particular role of drug use in its etiology and continued enactment. Using a theoretical approach derived from prior research and theory in both the drug use and delinquency fields, general hypotheses to be tested concern (1) the degree of drug involvement among seriously delinquent youths, (2) the nature of the drugs-crime relationship among adolescents, including by comparison with that among adults, and in terms of its consequences for subsequent relationships to conventional society, and thus (3) the role of drug use in determining which delinquent youths become adult career criminals rather than following the more usual pattern of dropping out of crime to become conventional adults. The methodology of the proposed study entails street interviews with 600 seriously delinquent youths in a major metropolitan area, using instruments adapted from those used with some 1500 adult offenders in prior phases of the study in the same community. Data analysis plans emphasize testing and post-test analysis of the hypotheses to obtain empirical support for the theoretical perspective proposed, to extend the theory where appropriate, to describe future drugs-delinquency research needs, and to explore the implications of the findings for public policy regarding adolescent drug use and serious delinquency.